Why Should I Mulch My Plants and Trees?

What Does Mulch Do For You?

What doesn’t it do? No, seriously, it does just about everything good that you can think of for trees and plants. Mulching your plants with wood chips gives you the following benefits:

  • Keeps weeds down
  • Retains moisture for longer
  • Reduces watering frequency and quantity
  • Prevents erosion
  • Increases water infiltration
  • Provides nutrients to the tree/plant
  • Prevents splashing which keeps soil borne diseases from spreading
  • Encourages deeper roots which aids drought tolerance
  • Increases organic matter in the soil
  • Reverses soil compaction
  • Encourages mycorrhizae and other beneficial bacteria and fungi
  • Moderates soil temperature

When it comes to mulching I just can’t think of a reason to not mulch. Not only are wood chips easily attainable, but they can be free from local arborist and tree trimming companies looking for a place to dump their tree trimmings.

Myths About Wood Chip Mulching

There is a lot of misinformation about the potential harm of mulching with wood chips. Below I’ll explain some of the common worries and what the research says about them.

Wood Chip Mulches Tie Up Nitrogen

This is a common misunderstanding that research has debunked multiple times.

“Apparently, there is no immediate nutrient binding danger from surface wood mulches of the particle size
that was used in this experiment.”

by Katrina M. Greenly and Donald A. Rakow

Certain types of mulches such as cypress, pine bark, or eucalyptus mulch by themselves increased soil K
or Mg concentrations, but none affected soil N concentrations.

Effects of Mulch Type and Fertilizer Placement on Weed Growth and Soil pH and Nutrient Content
Timothy K. Broschat

Wood Chips Are A Fire Hazard

Coarse wood chips can be ignited (most tests used a torch to do so as a cigarette butt or briquette wouldn’t ignite them), but it is the least flammable of the organic mulches. Rock and grass would be preferable to any other mulches if you were to only consider fire hazards. Rubber mulch, on the other hand, is the most flammable of any tested material. For more information see the links to the research itself below:


Woody Mulches Will Acidify Soil

Conflicting research shows this is true and false, but where we live a more acidic soil would be welcomed. One study concluded that pH can be effected based on both the mulching material and the soil composition type:

Wood Mulch Has Allelopathic Chemicals That Kill Other Plants

The only wood that has had significant allelopathic chemicals that would harm existing plants is black walnut. The rest that might have allelopathic chemicals may reduce the potential for seed germination, but do no harm to existing plants or plants that are past the seedling stage.

Diseased Tree Will Transfer Disease Through Wood Chips

This is a common worry of gardeners. While a pathogen from a chipped tree could last up to 2 years in the wood chips (not always true for all pathogens), the ability for that pathogen to exist and then transfer to another plant is unlikely.

However, just because a plant pathogen can be isolated from infested wood chips does not mean that the pathogen
in these wood chips can infect and incite disease in nearby healthy trees. A specific plant pathogen, a susceptible plant
host, and delimited environmental conditions are necessary for disease development

by Ronda Koski and William R. Jacobi

The truth is that wood chip mulch is the best overall mulch that you can put down. The few and almost nonexistent cons to wood chip mulch are heavily outweighed by the massive amount of benefits it provides for your plants.